1. Field of the Invention
The present invention relates, in general, to lenses of face protectors, and, in particular, to lenses of welding masks or helmets.
2. Related Art
Welding helmets or masks are headgear used when performing certain types of welding to protect the eyes, face and neck from flash burn, ultraviolet light, sparks and heat. Welding helmets are necessary to prevent arc eye, a painful condition where the cornea is inflamed. Welding helmets can also prevent retina burns, which can lead to a loss of vision. Both conditions are caused by unprotected exposure to the highly-concentrated UV rays emitted by the welding arc (which can also damage uncovered skin, similar to a sunburn).
All welding helmets include a small window, called a lens, through which the welder looks at the weld. In older helmets, the window can be made of darkly tinted glass, or perhaps a pair of polarized lenses. In more modern helmet designs, transparent material that darkens automatically when exposed to the flare of a welding arc are more common. Either type, however, is susceptible to damages such as cracks that can compromise the protection from ultraviolet rays. In addition to the lens shade, the helmet has a shroud around the face to protect it from hot metal sparks generated by the arc.
The hot metal sparks generated by the arc can ignite flammable objects in the welding area. Because the welding helmets include a small window directly in front of the welder's eyes and have obstructed peripheral vision or even no peripheral vision, a welder may not recognize that the hot metal sparks generated a fire in the area (e.g., to the sides) of the welder. The obstructed peripheral vision also prevents the welder from clearly seeing the future direction of their welding line, and they also may not see potential dangers such as people walking up to them from the side or objects moving or falling into their path.